A wireless telecommunications network provides wireless telecommunications service to users of mobile stations (e.g., “smartphones”, etc.) within a geographic region. The salient advantage of wireless telecommunications over wireline telecommunications is the mobility that is afforded to the user of the mobile station. On the other hand, the salient disadvantage of wireless telecommunications lies in that fact that because the mobile station is mobile, an interested party might not be able to readily ascertain the location of the mobile station.
There are many techniques in the prior art for estimating the location of a mobile station. The common theme to these techniques is that the location of the mobile station is estimated based on the electromagnetic (e.g., radio, etc.) signals—in one form or another—that are processed (i.e., transmitted or received) by the mobile station.
In accordance with one family of techniques, the location of a mobile station is estimated based on the transmission range of the base stations with which the mobile station is communicating. Because the range of a base station is known to be N meters, this family of techniques provides an estimate for the location that is generally accurate to within N meters. A common name for this family of techniques is “cell identification” or “cell ID.”
In accordance with a second family of techniques, the location of a mobile station is estimated by analyzing the angle of arrival or time of arrival of the signals transmitted by the mobile station. A common, if somewhat inaccurate, name for this family of techniques is called “triangulation.”
In accordance with a third family of techniques, the location of a mobile station is estimated by a receiver in the mobile station that receives signals from satellites in orbit. A common name for this family of techniques is “GPS,” which stands for “global positioning system.”
In accordance with a fourth family of techniques, the location of a mobile station is estimated by pattern matching one or more location-dependent traits of one or more electromagnetic signals that are processed (i.e., transmitted and/or received) by the mobile station. Common names for this family of techniques include “Wireless Location Signatures,” “RF Pattern Matching,” and “RF Fingerprinting.”
The basic idea behind the Wireless Location Signatures technique is that some traits of an electromagnetic signal remain (more or less) constant as a signal travels from a transmitter to a receiver (e.g., frequency, etc.) and some traits change (e.g., signal strength, relative multi-path component magnitude, propagation delay, etc.). A trait that changes is considered a “location-dependent” trait. Each location can be described or associated with a profile of one or more location-dependent traits of one or more electromagnetic signals. A mobile station at an unknown location can observe the traits and then attempt to ascertain its location by comparing the observed traits with a database that correlates locations with expected or predicted traits. Advantages of the Wireless Location Signatures technique are that it is highly accurate and works well indoors, in heavily-wooded forests, and in urban canyons.
Parties who are interested in knowing the location of a mobile station might include both the user of the mobile station and remote parties. There are a variety of reasons why the user of a mobile station might be interested in knowing his or her location. For example, the user might be interested in telling a remote party where he or she is or the user might seek advice in navigation.
In addition, there are a variety of reasons why a remote party might be interested in knowing the location of the user. For example, the recipient of an 9-1-1 emergency call from a user might be interested in knowing the location of the mobile station so that emergency services vehicles can be dispatched to the user. On the other hand, law enforcement might be interested in knowing the location of the mobile station if the mobile station user is a crime suspect.
For example, and in regard to law enforcement as an interested party, systems and methods are disclosed in U.S. Pat. No. 8,351,297 for processing information associated with monitoring persons/devices and weapon fire location information. When a device, such as a mobile station, is found nearby a gunshot location, associated graphical information can be presented on the output of the weapon fire location system or an associated display used by those monitoring the persons of interest.